In various buildings, concrete-sash joints and peripheries of glazing are generally sealed by applying or filling with sealing materials such as synthetic rubber or the like. Known sealing materials include materials based on silicone, polysulfide, modified silicone, polyurethane, acrylic rubber, SBR, butyl rubber and the like. Due to adhesion, heat resistance and weather resistance, silicone-based sealing materials of the condensation cure type are widely used. The basic properties required for such silicone-based sealing materials are non-sag property and fatigue endurance as well as weather resistance.
It is known that the use of sag control agents such as polyethers and the type of filler largely contribute to the non-sag property. In general-purpose silicone sealing materials currently used in the art, treated dry silica and surface treated colloidal calcium carbonate are predominant fillers. With regard to combinations of fillers with sag-control agents, U.S. Pat. No. 4,261,758 or JP-B 2-48586 disclose a combination of dry silica and a polyether with a molecular weight of 300-100,000. U.S. Pat. No. 4,304,897 or JP-A 1-245057 describes a combination of dry silica whose surface has been pretreated with octamethylcyclotetrasiloxane and a copolymer of polysiloxane and polyether which are linked through carboxyl groups. JP-A 61-21158 discloses a combination of a polyether having hydrolyzable silyl groups at both ends and a filler. JP-A 62-135560 discloses a combination of a polypropylene glycol having ketoxime groups at both ends and fumed silica. There remains a desire to have RTV organopolysiloxane compositions having further improved non-sag property.